The invention relates to a method for separating overspray from the overspray-laden booth exhaust air of coating systems, particularly painting systems, in which the overspray is taken up by an air stream and conveyed to an electrostatically operating separating device where the bulk at least of the solids is separated from the overspray on at least one separating surface.
The invention moreover relates to a device for separating overspray from the overspray-laden booth exhaust air of paint systems having    a) at least one separating surface along which the booth exhaust air can be conveyed and which is connected to a terminal of a high voltage source;    b) an electrode device which is arranged in the air stream, is associated with the separating surface and is connected to the other terminal of the high voltage source.
The invention furthermore relates to a system for coating, particularly painting, objects, particularly vehicle bodies, having    a) a coating booth in which the objects can be acted upon by coating material and through which an air stream can be conducted, which takes up and removes resultant overspray particles of the coating material;    b) an electrostatically operating separating device.
When paints are applied manually or automatically to objects, a substream of the paint, which generally contains both solid bodies and/or binding agent as well as solvent, is not applied to the object. This substream is known among experts as “overspray”. The overspray is taken up by the air stream in the paint booth and supplied for separation so that, if required, the air can be conveyed back to the coating booth after suitable conditioning.
Particularly in systems with a relatively high paint consumption, for example in systems for painting vehicle bodies, wet separation systems are preferably used. In commercially known wet separators, water flows together with the booth exhaust air coming from above to a nozzle accelerating the air stream. A swirling of the through-flowing booth exhaust air with the water takes place in this nozzle. During this procedure, the overspray particles largely pass over into the water so that the air exiting the wet separator has been substantially cleaned and the paint overspray particles remain separated in the water. They can then be recovered from this or disposed of.
In known wet separators, a relatively high amount of energy is needed to circulate the very large quantities of water required. Treating the rinsing water is costly due to the elevated use of paint-binding and detackifying chemicals and the disposal of paint sludge. Furthermore, as a result of the intensive contact with the rinsing water, the air absorbs a great deal of moisture which, in recirculating-air mode, in turn leads to a high energy consumption for treating the air.
In contrast, in commercially known devices of the type mentioned at the outset, a dry separation process is used in that paint overspray particles which are entrained by the booth exhaust air flowing past are ionised by the electrode device and, owing to the electrical field established between the separating surface and the electrode device, migrate to the separating surface on which they are separated. The paint overspray particles adhering to the separating surface can then be stripped off this mechanically, for example, and transported away.
The cleaning effect of such separators is very good. However, for continuous operation, it is necessary to always ensure that a sufficiently strong electrical field can build up between the separating surface and the electrode device, which is only possible up to a certain layer thickness of paint overspray on the separating surface, since such a layer has an insulating effect. However, the necessary continuous removal of the paint overspray from the separating surface involves complex structural measures and can be prone to faults. It is moreover possible that overspray will react, harden or dry on the separating surface so that it can no longer be simply removed by being stripped off the separating surface.